1. Field of Invention
The present invention relates to a timepiece, and relates more particularly to a sound emission structure for a timepiece that has an internal sound source and a communication opening rendered at the outside case member for emitting the sound produced by the sound source.
2. Description of Related Art
A structure having a gas-permeable waterproof film disposed between an audio device and a channel that communicates with the outside as the waterproof structure of a timepiece that has an audio device such as a speaker or microphone is known from the literature (see, for example, Japanese Unexamined Patent Appl. Pub. JP-A-H11-133157).
Wristwatches that use a piezoelectric vibrator as a sound source, attach the back cover with a waterproof film between the back cover and the case member, enable hearing the sound produced by the piezoelectric vibrator either through the back cover or a sound emission opening disposed between the back cover and the case member, and maintain the required waterproofness by means of the waterproof film, are also known from the literature (see, for example, Japanese Unexamined Patent Appl. Pubs. JP-A-H08-334574 and JP-A-H09-318774).
Various other structures for maintaining the required waterproofness while enabling sound to be output from a speaker, for example, in electronic devices other than timepieces are also known from the literature (see, for example, Japanese Unexamined Patent Appl. Pub. JP-A-2001-345907 and JP-A-H10-126713).
A problem with the sound emission structures of the timepiece and electronic devices described above is that while these structures can sufficiently externally transmit sounds with a high sound pressure such as from a speaker, they cannot efficiently guide sounds with a low sound pressure, such as reverberation (echoes) from a bell, to the outside, and the audible sound pressure range and sound quality are therefore limited.